Company Earning Per Share - Schedule of Computation of Basic and Diluted Net Income Per Share (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Earnings Per Share [Abstract]
Net income	$ 27,614	$ 21,170	$ 48,004	$ 43,035
Noncontrolling interests - consolidated real estate entities	(58)	(35)	(55)	(41)
Noncontrolling interests - Operating Partnership	(68)	(56)	(120)	(115)
Dividends to preferred shareholders	(922)	(922)	(1,844)	(1,844)
Unvested restricted stock (allocation of earnings)	(61)	(48)	(99)	(94)
Net income available to common shareholders	$ 26,505	$ 20,109	$ 45,886	$ 40,941
Weighted average shares outstanding - basic	54,464	53,773	54,450	53,430
Dilutive shares from stock options	194	323	198	369
Weighted average shares outstanding - diluted	54,658	54,096	54,648	53,799
Basic	$ 0.49	$ 0.37	$ 0.84	$ 0.77
Diluted	$ 0.48	$ 0.37	$ 0.84	$ 0.76